Recently, a storage device including a NAND flash memory (hereinafter referred to as a NAND memory) as a nonvolatile memory, for example, a solid-state drive (SSD) system is widely used in electronic equipment or the like.
The communication speed between an SSD and an initiator required for the SSD is higher than the communication speed between a hard disk drive (HDD) and an initiator and the communication speed is an extremely important factor in enhancing the performance. As a method for increasing the communication speed between the SSD and the initiator, a method for forming a Serial Attached SCSI (SAS) interface in a Wide Link form is provided. A plurality of signals can be simultaneously transferred by physically connecting the SSD and the initiator via a plurality of SAS cables.
In the SAS interface formed in the Wide Link form, two sets of phy/link/port/transport layers are provided in each port. Transmission data generated in one of the transport layers can be transmitted from a desired one of the phy layers and reception data to be transferred to one of the transport layers can be received from a desired one of the phy layers. It is extremely important how to efficiently use the phy layers provided two for each port.